Conventionally, a measuring method has been used which includes, for analyzing material characteristics, holding an object on a void-arranged structure, applying electromagnetic waves to the void-arranged structure on which the object is held, and analyzing the resulting transmittance spectra to measure characteristics of the object. Specifically, for example, terahertz waves are applied to a metal mesh having an object (e.g., protein) deposited thereon to analyze the resulting transmittance spectra.
Japanese Unexamined Patent Application Publication No. 2007-010366 (Patent Literature (PTL) 1) and Japanese Unexamined Patent Application Publication No. 2007-163181 (PTL 2) each disclose a method which includes a void-arranged structure having void regions (e.g., metal mesh), an object on the void-arranged structure, an electromagnetic-wave emitting unit configured to emit electromagnetic waves toward the object, and a detecting unit configured to measure the electromagnetic waves transmitted through the void-arranged structure. This method measures characteristics of the object on the basis of the fact that a frequency characteristic is changed by the presence of the object.
Japanese Unexamined Patent Application Publication No. 2008-185552 (PTL 3) discloses a method in which electromagnetic waves emitted from an electromagnetic-wave emitting unit toward a void-arranged structure are incident at an angle on a flat surface containing void regions, and characteristics of an object are measured by focusing on a frequency shift of a dip waveform appearing in a frequency characteristic of a measured value.
The methods for measuring characteristics of an object disclosed in PTL 1 to PTL 3 involve measuring not only a frequency characteristic obtained when the object is present, but also measuring, as a reference, a frequency characteristic obtained when no object is present (i.e., when a void-arranged structure alone is provided) (e.g., see FIG. 9 in PTL 3). These methods may further involve measuring a frequency characteristic obtained when no void-arranged structure is provided (i.e., measuring a frequency characteristic of a background). This means that in these methods, characteristics of an object are measured as the amount of change from a reference value.    PTL 1: Japanese Unexamined Patent Application Publication No. 2007-010366    PTL 2: Japanese Unexamined Patent Application Publication No. 2007-163181    PTL 3: Japanese Unexamined Patent Application Publication No. 2008-185552